Cathode materials having high energy density and lithium secondary battery containing the same

Abstract

Disclosed is a cathode material comprising a mixture of an oxide powder (a) defined herein and an oxide powder (b) selected from the group consisting of an oxide powder (b1) defined herein and an oxide powder (b2) defined herein and a combination thereof wherein a mix ratio of the two oxide powders (oxide powder (a): oxide powder (b)) is 50:50 to 90:10. The cathode material uses a combination of an oxide powder (a) and 50% or less of an oxide powder (b) which can exert high capacity, high cycle stability, superior storage stability and high-temperature stability, thus advantageously exhibiting high energy density and realizing high capacity batteries.

Description

TECHNICAL FIELD [0001]The present invention relates to a cathode material with a high energy density and a lithium secondary battery comprising the same. More specifically, the present invention relates to a cathode material comprising a mixture of an oxide powder (a) having a specific composition and an oxide powder (b) having a specific composition, wherein a mix ratio of the two oxide powders (oxide powder (a): oxide powder (b)) is 50:50 to 90:10.BACKGROUND ART [0002]In recent years, chargeable and dischargeable secondary batteries are widely used as energy sources of wireless mobile equipment. Of these, lithium secondary batteries are generally used due to advantages such as high energy density, discharge voltage and power stability.[0003]Lithium secondary batteries use metal oxide such as LiCoO2 as a cathode material and carbon as an anode material and are fabricated by inserting a polyolefin-based porous membrane between an anode and a cathode and swelling a non-aqueous electr...

AI Technical Summary

Benefits of technology

[0009]One object of the present invention is to provide a cathode material exhibiting a high energy density and superior capacity properties.

[0099]For example, the laminate sheet may have a structure including an inner resin layer, a blocking metal layer and an outer resin layer. The outer resin layer should have tensile strength and weatherability equal to or higher than a predetermined level in order to secure superior resistance to external environments. In this regard, the polymer resin for the outer resin layer is preferably a polyethylene terephthalate (PET) and drawn nylon film. The blocking metal layer is preferably aluminum to prevent incorporation and leakage of foreign materials such as gas and humidity and improve strength of the battery case. The polymer resin for the inner resin layer is preferably a polyolefin resin which has thermal fusion (thermal adhesion) and low absorbance in order to inhibit invasion of the electrolyte and is not swollen or precipitated by the electrolyte, more preferably undrawn polypropylene (CPP).

Problems solved by technology

LiCoO2 has several disadvantages of being relatively expensive, having low charge / discharge capacity of about 150 mAh / g and unstable crystal structure at a voltage of 4.3 V or higher and the risk of reacting with an electrolyte to cause combustion.

Furthermore, LiCoO2 is disadvantageous in that it undergoes great variation in physical properties depending upon variation in parameters in the preparation process thereof.

Secondary batteries comprising such a cathode material exhibit low stability at high electric potential or have a limitation of application to mass-production.

Use of secondary batteries is expected to further increase and the above problems and problems associated with stability of batteries and high-temperature storage properties at high electric potentials arise.

However, conventional mixture-type cathode materials have a limitation of the difficulty of obtaining superior synergetic effects to the case of simple combination of two ingredients.

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